1. Field of the Invention
The present invention relates to a production method for a complex polyester composition. Specifically, the present invention relates to a production method for polyester in which specific polyester is condensed in the absence of a solvent, and a complex polyester composition of which a specific component having an area of less than or equal to a certain value in a GPC chart is produced.
2. Description of the Related Art
In general, a lubricant contains base oil and various additives. Examples of the base oil include mineral oil obtained from crude oil, ester-based oil which is chemically synthesized, fluorine oil, polyalphaolefin-based oil, and the like. Among them, the ester-based oil is preferably used in a jet plane, automobile engine oil, grease, and the like from the viewpoints of a low fluid point, a high viscosity index, a high flash point, excellent lubrication performance, biodegradability, and the like.
Various esters such as monoester obtained from a reaction between an aliphatic monocarboxylic acid and monohydric alcohol; diester obtained from a reaction between an aliphatic dibasic acid and monohydric alcohol; ester obtained from a reaction between polyhydric alcohol and an aliphatic carboxylic acid; and complex ester obtained from a reaction between polyol, a polybasic acid, and an aliphatic monocarboxylic acid, have been disclosed as the ester-based oil (JP2002-097482A, JP2005-154726A, JP2005-232434A, JP2005-213377A, and JP2005-232470A).
Recently, the lubricant has been required to have high lubrication performance according to diversification and advancement of the industrial field. For this reason, development of polyester having excellent lubrication performance has progressed. For example, in JP2011-89106A, a polyester composition which is obtained by a reaction between polyhydric alcohol, a polycarboxylic acid, and monohydric alcohol having an oxyalkylene group is disclosed. Here, a condensation reaction of the polyester composition is performed in the presence of a solvent.